Metz1234

I have a 1977 Scarab 300 with factory twin 350's and TRS drives. Starboard motor is running hot, pulled seawater pump no damage went ahead and put new impeller in and new thermostat and motor is still running hot (no noticeable steam out the back and no water in oil), seems to have plenty of water coming out the back. Temp on exhaust is about 200 on both sides and risers are about 90 to 100 or so. Port motor is about 100 on exhaust and risers about 90 or so. I pulled exhaust and everything is clean and no scaling at all. I am struggling with this and could use any advice on this. I am new to the TRS drives and have not checked the flapper or anything waiting on manual in the mail. The exhaust to riser gasket has the water jackets blocked off on both sides of the exhaust. Boat came from the Ozarks and was in a barn in Conroe for 10 years or so and previous owner pulled heads and had them reworked because both cams were flat from original owner not setting valves correctly. So new cams, heads reworked, new intake and 4brl carbs transmission cooler is routed out the back and not thru exhaust anymore and has great flow. Sorry for all the info but more is better.

airjunky

iTrader: (2)

Its reading and is hot in the thermostat housing ,both manifolds on that motor are too hot to keep a hand on ,but the risers are normal temp? Are those the old brick style rear exit? Amazing there not clogged.
Does it get hot idling at the dock and just get hotter when moving the boat under a load? Do you have enough room in there to have your pump draw water out of a bucket or pan on the trailer to check the flow? How about flipping your inner 2 exhaust water dump hoses port to starboard and monitor those manifold temps,
Grab a water pressure gauge and use that ,to find restrictions , sounds like you have already ruled out a trans issue spiking your inlet raw water temps

Blueabyss

Post a pic of your exhaust manifolds and your thermostat housing. If you can also post a pic of those gaskets.

Chris

Griff

What are the water temp guages reading???????????

Are you running on a hose or in the water????

BUP

iTrader: (9)

check balls stuck if applicable in t stat housing or water circ pump. Also are all water jackets completely non restricted in the exhaust system. Wrong riser gaskets ?

Metz1234

problem started in water and now troubleshooting off the hose, lake is not real convenient to run this boat in (Lake Houston) its normally on Conroe but will be on Rayburn after this fix. I can probably pull out of bucket with raw water pump I will try that. The Temp rises faster under a load and take a long time to cool down idling but is still hot, running at dock or off a hose temp comes up pretty fast. The temps I posted were after running off a hose at idle for 15 min. I brought a Bore scope home and plan on looking in manifolds and looking to see If flapper is where it needs to be, I don't have thru hull exhaust so all exhaust goes thru drive. Next step is swap some hose like mentioned by Airjunky and probably pull circulating pump and back flush thru block. First time to post pics on forum so if this does not work I will try something else.....

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Metz1234

I am going to pull riser on the other motor and check to see if its the open water jacket or closed tomorrow.

mike tkach

iTrader: (3)

check the p/s and oil coolers for junk clogging them.

Blueabyss

No expert on that style manifold but it seems odd that there is a block off gasket between the manifold and riser. Usually thats for closed cooling systems. Do the risers have separate hoses coming off the T stat housing that go to them.

Chris

airjunky

iTrader: (2)

Looks pretty clean for some old school manifolds from way back in the day.
A good trs pump will way exeed what a garden hose will deliver, go for the bucket with hose (or2) feeding it .